The invention relates to a dictation apparatus for storing a speech signal in addressable memory means and to a transcription apparatus for transcribing speech messages. A dictation apparatus as defined in the opening paragraph is well known in the art. Reference is made in this respect to EP-A 65,148, document (4) in the list of related documents.
Data compression may be realized in prior art dictation apparatuses by discarding the silence periods normally present in the speech signal. Further, one may store an indication signal indicating the length of the silence period and its location in the speech signal. Upon transcription, a replica of the speech signal can be regenerated by inserting silence periods of the same length at the indicated positions in the compressed speech signal.
Sometimes an insert need to be added to a speech signal stored earlier in the memory means. EP-A 65,148 describes a way how to enable an insert to be stored in the memory means.
The invention aims at providing an improved dictation apparatus. The dictation apparatus in accordance with the invention is characterized in that the device comprising
input means for receiving the speech signal,
data compression means for data compressing the speech signal into a data compressed speech signal, the data compression means being adapted to carry out a data compression step on the speech signal in one of at least two different data compression modes, the at least two different data compression modes resulting in different data compression ratios when applied to the same speech signal, the said at least two different data compression modes being selectable by a user, the data compression means being further adapted to create data files comprising a data compressed speech signal, the data files comprising a header portion, the data compression means being also adapted to generate an identifier signal identifying the data compression mode selected and being adapted to store said identifier signal in said header portion,
storing means for storing the data files in the memory means, the storing means comprising address generator means for generating addresses for said addressable memory means, for storing blocks of information comprised in a data file in the memory means,
control means selectively operable by a user for providing an insert signal and an end of insert signal,
pointing vector generator means for generating a block of at least two and at most three pointing vectors in response to the occurrence of each insert signal, said block of pointing vectors comprising a first address signal corresponding to the address generated by the address generator means upon the occurrence of the insert signal and a second address signal corresponding to a beginning address of an available portion of said addressable memory for storing a dictation insert.
The invention is based on the following recognition. The memory capacity of memories included in dictation apparatuses is limited. Preferably, an increased number of dictations should be stored in a memory. This has been realized in the prior art by leaving out the silence periods present in a speech signal. A larger compression ratio can be obtained by applying more powerful compression techniques. More specifically, lossy compression techniques result in large data compression ratios. Larger data reduction ratios, however, may lead to a decrease in quality of the retrieved signal upon data expansion. In accordance with the invention, a dictation system has been proposed in which the user has the possibility to choose one data compression mode from two or more data compression modes in which the dictation apparatus can compress the speech signal. The user can make a trade off between the number of speech messages that he wants to dictate and store in one memory unit and the quality of the speech signal upon reproduction. If the user wants to have more dictations stored in the memory, he will select the data compression mode giving a higher data compression ratio. If the user prefers a higher quality of reproduction, he will choose the data compression mode giving a lower data compression ratio.
Further, storing an insert in the memory means is realized by storing two, or in another embodiment, three pointing vectors at the maximum for each insert to be stored in the memory means. This has an advantage over the prior art dictation apparatus, which requires the storage of a jump signal at the location in the originally stored speech signal where the insert should be made, thereby overwriting a portion of the original speech signal stored, a jump signal at the end of the stored insert and four pointing vectors linking the two addresses from which a jump should take place to the two addresses where the jumps should end.
Contrary to this, in one embodiment of the invention, only two pointing vectors are required, linking the address in the originally stored speech signal where the insert should be made and the address corresponding to a beginning address of an available portion of said addressable memory for storing a dictation insert. At the end of the insert, an end-of-file signal could bestored, which can be used as jump instruction upon reproduction so as to jump back to the position of the insert in the original speech message.
In another embodiment, exactly three pointing vectors are stored in a block of pointing vectors, the third address signal corresponding to the address generated by the address generator means upon the occurrence of the end of insert signal. Upon reproduction in the transcription apparatus, the addresses generated by the address generator means are compared to the first address signal so as to activate the first jump from the location of the insert in the originally stored speech signal, which corresponds to this first address signal, towards the location where the beginning of the insert is stored, which corresponds to the second address signal, upon equality of the generated addresses with the first address signal. The addresses generated by the address generator means are further compared to the third address signal so as to activate a second jump from the location where the end of the insert is stored, which corresponds to the third address signal, towards the location of the insert in the originally stored speech signal, which corresponds to the address subsequent to the first address, upon equality of the generated addresses with the third address signal.
The various subclaims define preferred embodiments of the dictation apparatus and the transcription apparatus in accordance with the invention.